It is known that 802.11 relates to a family of specifications developed by the IEEE for wireless LAN technology and specifies an over-the-air interface between a wireless client and a base station or between two wireless clients. In one form, 802.11 applies to wireless LANs and provides 1 or 2 Mbps transmission in the 2.4 GHz band using either frequency hopping spread spectrum (FHSS) or direct sequence spread spectrum (DSSS). Of the several specifications in the 802.11 family, 802.11b (also known as 802.11 High Rate or Wi-Fi), refers to an extension to 802.11 that applies to wireless LANS and provides 11 Mbps transmission (with a fallback to 5.5, 2 and 1 Mbps) in the 2.4 GHz band. It is also known that 802.11b generally uses only DSSS and provides wireless functionality comparable to Ethernet. 802.11g in its application to wireless LANs provides 20+ Mbps in the 2.4 GHz band. 802.11b has a maximum raw data rate of 11 Mbit/s and uses the same CSMA/CA media access method defined in the original standard. Due to the CSMA/CA protocol overhead, in practice the maximum 802.11b throughput that an application can achieve is about 5.9 Mbit/s over TCP and 7.1 Mbit/s over UDP. 802.11b operates in the 2.4 GHz RF spectrum. Hence, metal, water, and thick walls absorb 802.11b signals and might decrease the range drastically. For DSSS (Direct Sequence Spread Spectrum) modulation, 802.11b uses BPSK (Binary Phase Shift Keying) for 1 Mbit traffic and QPSK (Quad-Phase Shift Keying) for 2 Mbit traffic. For higher data rate traffic it uses QAM (Quad-Amplitude Modulation) modulation. With high-gain external antennas, the protocol can also be used in fixed point-to-point arrangements, typically at ranges up to eight kilometers or longer where a line of sight is available. For security, WEP (Wireless Encryption Protocol/Protection) is used generally.
The 802.11g standard is designed as a higher-bandwidth—54M bit/sec—successor to the popular 802.11b, or Wi-Fi standard, which tops out at 11M bit/sec. Generally, an 802.11g access point will support 802.11b and 802.11g clients. Similarly, a laptop with an 802.11g card will be able to access existing 802.11b access points as well as new 802.11g access points. The 802.11 standard refers to a general MAC-layer and three different PHY-layers. The MAC-layer is the same for all the PHY-layers. The MAC layer is also responsible for fragmentation and encryption. It is known that MAC protocols in some applications arbitrate access to a shared channel among several users. MAC layer management is responsible for synchronization, power management, roaming and MAC-M1B. The standard as relating to Wireless LAN also defines two types of wireless networks, the first one being known as BSS (Basic Service Set). The BSS is a wireless network and is normally built up of PCs (or notebooks) with a wireless network card. The second one is the ESS (Extended Service Set) and is also called an ‘Ad Hoc’ network and connects the wireless stations to a wired network through one or more access points. The access point is actually a bridge between a wired network and a wireless network. The Medium Access Control (MAC) protocol is used to provide the data link layer of the Ethernet LAN system. The MAC protocol in one form encapsulates a SDU (payload data) by adding a 14 byte header (Protocol Control Information (PCI)) before the data and appending a 4-byte (32-bit) Cyclic Redundancy Check (CRC) after the data. The entire frame is preceded by a small idle period (the minimum inter-frame gap, 9.6 microseconds (μS)) and an 8 byte preamble. The purpose of the idle time before transmission starts is to allow a small time interval for the receiver electronics in each of the nodes to settle after completion of the previous frame. A node starts transmission by sending an 8 byte (64 bit) preamble sequence. This consists of 62 alternating 1's and 0's followed by the pattern 11. Generally, the last byte which finishes with the ‘11’ is known as the “Start of Frame Delimiter”, herein referred to as SFD. The SFD field of a frame indicates the beginning of a frame being transmitted. Typically, the SFD may consist of a one octet field that marks the end of the timing information and may contain the bit sequence 10101011. The octet field may be used both for synchronization and start of frame delimiting. Upon receipt of a frame, its frame check sequence may be checked for damage using CRC (cyclic redundancy check). In the context of 802.11, a preamble provides a clock at the start of each packet, which allows the receiving devices to lock the incoming bit stream. The preamble might use either an SFD or a synch field to indicate to the receiving station that the data portion of the message will follow. In one application, the preamble might comprise a preamble synchronization portion and an SFD portion. In the context of this invention, SFD is a pattern used for synchronization, and is usually known to be detected using descramble information taking an additional 7 uS.